We discuss a few selected aspects of MPEG-4 Systems which includes a representation of description of multimedia scenes, delivery of coded multimedia objects and the scene description, composition, and synchronized playback. We first present an overview of BIFS, the MPEG-4 scene description language, as well as a brief background of VRML, on which BIFS is based. We then discuss the basics of a (nonadaptive) MPEG-4 playback system, including issues in BIFS and media decoding. The state of the software implementation in MPEG-4 of the 2D scene player and the 3D scene player is then discussed. Thus, the novel aspects of MPEG-4 Systems version 1 work which is near completion, is reviewed. We also discuss related aspects of the ongoing work on version 2 of MPEG-4 Systems. This includes additional work on scene description, referred to as advanced BIFS, and work on JavaTM based extension of MPEG- 4 System to an adaptive system referred to as MPEG-J. The work on advanced BIFS, extends the version 1 scene description by a number of additional capabilities. The work on MPEG-J involves design of architecture to control version 1 system, and set of API. Thus, the status of some of the ongoing work on MPEG-4 Systems version 2 is also reviewed.